High-voltage device such as, for example, high-voltage transformers are very hot during operation due to the high levels of current and voltage. For this reason, the transformer windings are arranged in a so-called tank. This tank is hermetically closed and filled with a transformer oil. Through a cooling circuit, the transformer oil is used for the purpose of keeping the operating temperature low. However, during operation it is possible for the transformer oil to heat extremely rapidly as a consequence of, for example, winding short-circuits and to thereby expand. The expansion of the transformer oil can have the consequence that the tank does not withstand the pressure, uncontrollably ruptures and parts of the tank are flung around. In order to be able selectively compensate for a pressure rise of that kind pre-defined rupture locations in the form of burst discs are introduced into the tank, thus the housing of the high-voltage transformer.
High-voltage device safeguarded from pressure waves and filled with insulating liquid and/or with gas is known from DE 17 21 316 U. This high-voltage device has an opening that is closed by means of a burst disk. The burst disk consists of hard paper that is covered on the inner side by a metal foil. The hard-paper disk as well as the metal foil are screw-connected by a ring to the housing wall of the high-voltage device. The hard-paper disk is sealed relative to the housing wall and to the ring in each instance by a rubber sealing ring.
A particular disadvantage with this burst disk is the constructional format thereof and the material used. In order to protect the part that consists of hard paper, from the aggressive oil it is essential to use a metal foil. However, at the time of assembly it can easily happen that the metal foil is off-center, the aggressive oil penetrates to the hard-paper disk and the high-voltage device is no longer correctly sealed. A further disadvantage is that the hard-paper disk is very sensitive. During maintenance operations it can happen that an engineer unintentionally steps on the membrane and destroys this. A further problem with the hard-paper solution is the longevity thereof. Due to external influences the material can fatigue and rupture at even a small rise in pressure. Faulty triggering of that kind is connected with a high level of maintenance outlay and is thus undesirable. Since the hard-paper disk is formed homogenously over the entire area it cannot be predicted how this would rupture in the case of a sudden pressure rise.
A voltage converter with a surrounding casing as a protective device is known from DE 20 016 065 U1. Excess-pressure safety means is arranged on the upper side of the casing. The excess-pressure safety means is a burst protector with an opening closed by a burst film. On reaching a specific pressure in the voltage converter the burst film ruptures.
In the case of this burst protector as well, the material used is to be regarded as a weak point. Since the film is exposed to weathering, in the course of time material fatigue can occur. Thus, it is also possible here for the foil to rupture at significantly lower pressure than originally defined and undesired, faulty triggering to occur. Moreover, here as well, destruction of the burst film can occur due to inattention during maintenance operations, since this film is not protected from the action of force.